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UNITED STATES PATENT ()FFICE.*

HERMANN A. SEEGALL, OF BERLIN,GERMANY.

PROCESS OF MAKING GHROMIUM SULPHATES.

SPECIFICATION forming part of Letters Patent No. 415,739, dated November 26, 1889.

Application filed March 25, 1889. Serial No. 304,682. (No specimens.)

To all whom it may concern:

Be it known that I, HERMANN ALBERT SEE-- GALL, a subject of the King of Prussia, Grerbichromate, which formed the groundwork of The disintegration of chrome ores for the purpose of all other chrome preparations.

analyzing the same has been effected in the laboratory by means of melting them together with alkali bisulphate. This method is not, however, suitable for trade purposes,

since in order to secure a completedisinte.

gration of the ores a large excess of bisul- :phate is necessary, whereby through the development of sulphuric-acid vapors the lungs of the workmen are injuriously affected and only an imperfect utilization of the bisulphate is attained.

I have discovered that two important points in the process must be taken into account and carried out before the same can be employed with advantage for trade purposes. The first of-these two points consists in holding the chrome materials in suspension in melted alkali during the heating of the same, in order to impart toit a large surface of contact for the escaping sulphuric acid. The second of these important points is the regaining of the sulphuric-acid vapors (having escaped Without having taken part in the reaction) through condensation. These two points in the disintegration of theraw materials containing chrome combine to make my process capable of being used with advantage for'industrial purposes.

By my method, hereinafter described, I aim enabled to obtain a chromic sulphate in the form of a soluble chrome preparation direct from the raw materials, suitable for industrial purposes, which can then be worked on the other chrome preparations.

I pulverize thesubstance containing the chromium and heat it in receptacles pro% cooled condensers, where I obtain the sulphuric acid, while I take the remaining sulphurous acid into a receiver containing limemilk andobtain there calcium hyposulphite. The holding of the raw material in suspension during the heating, which is throughout necessary for the process, may not only be attained by means of stirring apparatus, but also by a shaking apparatus or revolving furnace.

In the process just described the only disadvantages are the necessity of carrying on the heating in covered receptacles, of condensing the escaping gases, and of having to work with a mechanical stirring arrangement of some sort.

I have further found that the quantity of the vapors produced during the heating or melting may be reduced to a minimum or entirely prevented if some quantity of a substance be introduced into the melted mass. The said substance must not melt or decompose at a temperature of 600 ceutigrade,

but only serve to make the melted mass more pulpy. The explanation of this result is the following:

of course only work upon the ore on coming into contact with the same. It cannot, however, come into contact with the ore if the same is lying on the bottom of the meltingpot and the sulphuric acid steaming away from-the upper surface of the contents of the pot. It is here that the advantage becomes apparent 'of inter-mixing a substance which neither melts nor decomposes nor precipitates at a temperature of 600 centigrade. The m'eltedmass is no longer so thin and the powdered ore is no longer able to sink to the bottom, but is held in close contact with the melted bisulphate, and is in consequence subjected to the influence of the sulphuric acid ing chromium (chrome slags) which when melted with bisulphate immediately cause the mass to assume athick pulpy nature; but they do not'remain suspended in the same, and in consequence require the aid of a mechanical stirring apparatus. If I take .9, specific gravity of the substance added, P absolute weight of the substance added, 8 specific gravity of the mixture set, G weight of the mixture set or melted, and 00 equal the quotient of the volume of the mixture set by the volume of the melted mixture, then G8 5 1s P: 85 and 00:

If 00 equal one, no addition is necessary.-

All substances which do not melt or decompose at the temperaturenecessary for the processviz., 600 centigrademay be used foradding to the mixture, particularly the oxides, hydra-ted oxides, non-volatile salts of the metals of the alkaline earths, and of the earthy metals and silicic' acid. In case it is not required to gain sulphuric acid as a byproduct, as in the process at first described, the condensers and stirring apparatus may be dispensed with. When mixing anyof the substances just mentioned to the melting mass, the decomposition of the materials containing chromium will be attained in the lastlydescribed manner.

I perform the process at first described in the following manner: One hundred parts of chrome ore and four hundred parts of sodium bisulphate are ground up very fine and thoroughly mixed. The mixture is then heated in covered receptacles provided with a stirring apparatus to 600 centigrade for the space of about two to two and one-half hours, by which means the chrome ore, since it is held in suspension, will be almost entirely decomposed, and-the amount of sulphuric acid corresponding to two hundred parts of bisulphate will be received in the condensers. The gases (80,) not condensed in the condensing apparatus will be arrested by the lime-milk. The melted mass is then cooled up and lixiviated with water.

I perform the second method by finely powdering and mixing one hundred parts of chrome ore with two hundred parts of sodium bisulphate and fiftyparts of barium sulphate and then heating the mixture to a temperature of 600 centigrade for about two to two and one-half hours. The quantity of vapors produced by this method is so insignificant that they may be allowed to escape. After the melting has taken place the mass will be removed from the melting-pot and lixiviated with water. If barium sulphate be not used as an addition, the minimum amount of the mass to be added may be obtained from the equation for P. In any case a material must be chosen which at 600 centigrade does not combine with the sulphuric acid set free. Should a material be employed for this pur- 9o pose which does combine with the sulphuric acid which is released, it is then always necessary to add bisulphate enough to satiate the requirements of the material added and then be sufficient to decompose the materials 5 containing the chrome. Accordingly s will in this case represent the specific gravity of the combination of the material added with sulphuric acid.

From the chrome sulphate which is contained in combination with other sulphates in the watery solution resulting from both methods it is now easily possible to obtain the hydrated oxide of chromium through precipitation by means of the well-known re- 5 agents, (such as caustic alkalies, alkaline carbonates, magnesia, &c.,)'when the hydrated oxide of chromium forms a porous easilyoxidizable mass. This hydrated oxide of chromium is certainly in the most cases impurified by the presence of hydrated oxide of aluminium and hydrated oxide of iron, from which it can, however, easily be separated, (for instance, by washing.) This hydrated oxide of chromium forms a much better es- 5 sential element for producing the other chrome preparations than the alkali bichromate used up to the present in the industry for the same purpose. For forming chrome salts from this hydrated oxide of chromium it is not necessary to make any reduction, as the hydrated oxide of chromium combines directly with acids to form salts of chromium. The oxidation for the formation of chromates can also be conveniently carried out, 5 since the hydrated oxide of chromium coinbines directly with bases forming the corresponding chromates. In the latter case the oxygen in co-operation with the impurifying hydrated oxides produces an advantageous 3 effect, while in the methods of carrying out the-oxidation up to the present in use impurities had a reducing effect on the melting mass.

In Working the oxidation according to my method not only a saving of time is effected, but also less firing material is required. It may be carried out much more easily and with far simpler and less expensive apparatus. Lastly, a much more complete using up of the materials employed is attained thanin those processes in use up to the present.

In the following claims I mean by the term acid sulphates of any fixed alkali not only the combination RHSO but all sulphates of fixed alkalies which with regard to the combination R SO 4 contain an excess of sulphuric acid.

Having thus fully declared the nature of my said invention, what I claim, and desire to secure by Letters Patent of the United States, is-

1. The process of manufacturing chromic or chromous sulphates from materials containing chrome by heating the said substances in covered receptacles with the acid sulphates of any fixed alkali,and holding the materials containing chrome continually in suspension in the melting mass by mechanical agitation, for the purpose and in the manner substantially as described.

2. The process of manufacturing chromic or chromous sulphates from materials c011- taining chrome by heating the said substances in covered receptacles with the acid sulphates of any fixed alkali, and holding the materials containing chrome continually in suspension in the melting mass by mechanical HERMANN A. SEEGALL.

lVitnesses:

B. ROI, THEoDoR HEESE. 

